It might sound like a joke, but when a married man went to the doctors with stomach cramps he found out that he was in fact having a period ... and that he was a woman.
The shocking discovery came when Mr Chen from Zhejiang, an eastern coastal province in China, complained of feeling constantly tired and found blood in his urine, according to Shanghaiist.com.
Upon visiting the doctors, he was immediately given a CT scan and told he had a uterus and ovaries.
Confused doctors then performed a chromosome examination, revealing Chen had a pair of XX sex chromosomes - meaning that, genetically, he was a woman.
Doctors also found he had no Adam's apple and his genitalia were "different."
The chief of the First People's Hospital of Yongkang said: "He was wearing men's clothes with short hair so we didn't think that he would be a female at the beginning."
Chen claimed that he had sexual intercourse with his wife, but doctors wondered how that was possible.
They concluded such medical cases were extremely rare and added that it was too late for Chen to receive medical treatment to reverse the abnormality, as it is only effective in younger people.